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AJvYcCV5QDZMkuu+sYNm2TkkszzVCXZY4CJcRB6NLcB8V3uV6NtwKEC+PR3LPgR6/IeLtfKDnP00@lists.linux.dev X-Gm-Message-State: AOJu0YxNtP7cbFyIpLO/h9mhCf9TcA0rLW7yq22KVVpvMNQUB141H0An D6SSKWb7k+BV8QdZV/AC+605gyqBx214M1OQcYt8+p6bp07R47QGIEdieVmoxps= X-Google-Smtp-Source: AGHT+IGl9omV9EQTehYn0SrRAnQbJvtu3xuf912k6OEP16tiWclCTW8yLnjvynJbx2lwFE1h7mD5Pw== X-Received: by 2002:a05:6e02:1648:b0:39f:5521:2cd4 with SMTP id e9e14a558f8ab-3a365959a2bmr34538815ab.26.1727885648258; Wed, 02 Oct 2024 09:14:08 -0700 (PDT) Received: from [192.168.1.116] ([96.43.243.2]) by smtp.gmail.com with ESMTPSA id e9e14a558f8ab-3a344d6073esm36800745ab.8.2024.10.02.09.14.05 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 02 Oct 2024 09:14:06 -0700 (PDT) Message-ID: <0fd31bb1-6b76-4d27-9365-4dedfc323b2c@kernel.dk> Date: Wed, 2 Oct 2024 10:14:05 -0600 Precedence: bulk X-Mailing-List: lkmm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 0/4] sched+mm: Track lazy active mm existence with hazard pointers To: Mathieu Desnoyers , Matthew Wilcox Cc: paulmck@kernel.org, Linus Torvalds , Andrew Morton , Peter Zijlstra , linux-kernel@vger.kernel.org, Nicholas Piggin , Michael Ellerman , Greg Kroah-Hartman , Sebastian Andrzej Siewior , Will Deacon , Boqun Feng , Alan Stern , John Stultz , Neeraj Upadhyay , Frederic Weisbecker , Joel Fernandes , Josh Triplett , Uladzislau Rezki , Steven Rostedt , Lai Jiangshan , Zqiang , Ingo Molnar , Waiman Long , Mark Rutland , Thomas Gleixner , Vlastimil Babka , maged.michael@gmail.com, Mateusz Guzik , Jonas Oberhauser , rcu@vger.kernel.org, linux-mm@kvack.org, lkmm@lists.linux.dev References: <20241002010205.1341915-1-mathieu.desnoyers@efficios.com> <8a627fc7-cc62-40e6-ad28-c730d4a8f7d6@efficios.com> <579bdbbf-82a7-4330-9a5e-495d89befbac@kernel.dk> Content-Language: en-US From: Jens Axboe In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/2/24 10:02 AM, Mathieu Desnoyers wrote: > On 2024-10-02 17:58, Jens Axboe wrote: >> On 10/2/24 9:53 AM, Mathieu Desnoyers wrote: >>> On 2024-10-02 17:36, Mathieu Desnoyers wrote: >>>> On 2024-10-02 17:33, Matthew Wilcox wrote: >>>>> On Wed, Oct 02, 2024 at 11:26:27AM -0400, Mathieu Desnoyers wrote: >>>>>> On 2024-10-02 16:09, Paul E. McKenney wrote: >>>>>>> On Tue, Oct 01, 2024 at 09:02:01PM -0400, Mathieu Desnoyers wrote: >>>>>>>> Hazard pointers appear to be a good fit for replacing refcount based lazy >>>>>>>> active mm tracking. >>>>>>>> >>>>>>>> Highlight: >>>>>>>> >>>>>>>> will-it-scale context_switch1_threads >>>>>>>> >>>>>>>> nr threads (-t) speedup >>>>>>>> 24 +3% >>>>>>>> 48 +12% >>>>>>>> 96 +21% >>>>>>>> 192 +28% >>>>>>> >>>>>>> Impressive!!! >>>>>>> >>>>>>> I have to ask... Any data for smaller numbers of CPUs? >>>>>> >>>>>> Sure, but they are far less exciting ;-) >>>>> >>>>> How many CPUs in the system under test? >>>> >>>> 2 sockets, 96-core per socket: >>>> >>>> CPU(s): 384 >>>> On-line CPU(s) list: 0-383 >>>> Vendor ID: AuthenticAMD >>>> Model name: AMD EPYC 9654 96-Core Processor >>>> CPU family: 25 >>>> Model: 17 >>>> Thread(s) per core: 2 >>>> Core(s) per socket: 96 >>>> Socket(s): 2 >>>> Stepping: 1 >>>> Frequency boost: enabled >>>> CPU(s) scaling MHz: 68% >>>> CPU max MHz: 3709.0000 >>>> CPU min MHz: 400.0000 >>>> BogoMIPS: 4800.00 >>>> >>>> Note that Jens Axboe got even more impressive speedups testing this >>>> on his 512-hw-thread EPYC [1] (390% speedup for 192 threads). I've >>>> noticed I had schedstats and sched debug enabled in my config, so I'll have to re-run my tests. >>> >>> A quick re-run of the 128-thread case with schedstats and sched debug >>> disabled still show around 26% speedup, similar to my prior numbers. >>> >>> I'm not sure why Jens has much better speedups on a similar system. >>> >>> I'm attaching my config in case someone spots anything obvious. Note >>> that my BIOS is configured to show 24 NUMA nodes to the kernel (one >>> NUMA node per core complex). >> >> Here's my .config - note it's from the stock kernel run, which is why it >> still has: >> >> CONFIG_MMU_LAZY_TLB_REFCOUNT=y >> >> set. Have the same numa configuration as you, just end up with 32 nodes >> on this box. > > Just to make sure: did you use other command line options when starting > the test program (other than -t N ?). I did not, this is literally what I ran: for i in 24 48 96 192 256 512 1024 2048; do echo $i threads; timeout -s INT -k 30 30 ./context_switch1_threads -t $i; done and the numbers I got were very stable between runs and reboots. -- Jens Axboe